Many photographic processes, including those in the graphic arts industries, utilize large amounts of water in various chemical solutions necessary in development and processing operations. This water is used to carry chemical reactants, preservatives, catalysts, accelerators and the like. The water also serves to wash away unwanted chemical by-products or unreacted chemicals from the finished film or paper. Many commerical size plants operating photographic processes can utilize as much as 150,000 U.S. gallons of water per day.
Heretofore, it has been conventional practice to discharge spent chemical solutions into municipal sewer systems and utilize fresh water to make new chemical solutions for use in the photographic process. This practice puts an enormous strain on the resources of the municipal water treatment plants. Additionally, in many countries throughout the world government authorities are carefully scrutinizing chemical discharge levels in industrial wastewater effluents. In some countries in the world, this scrutiny has lead to new legislation which bans or significantly reduces the discharge limits of chemicals in wastewater effluent. In the future, it is envisaged that there will be a complete ban on the discharge of any chemicals from industrial processes.
In the case of operators of commercial photographic processes such a ban could be fatal to the operation of the business. This is due to the fact that the photographic process industry consumes enormous amounts of fresh water and discharges a wastewater laden with environmentally hazardous heavy metals and organic compounds.
It would be desirable to have a process capable of substantially reducing the concentration of or eliminating the environmentally hazardous heavy metals and organic compounds from photographic process wastewater. Preferably, such a process would be efficient, relatively inexpensive and simple to operate.